The Gospels say little about the business of crucifixion. “And they crucified him” is all St. Mark offers (15:24), with no word of how it was done or how the cross tortured its victim.

The early Christians offered little more when they recited the Creed: “He was crucified under Pontius Pilate, suffered, died and was buried.”

The Crucifixion comes at the climax of the Christian drama. Yet tradition records the matter as little more than a fact. “They crucified him.” “He was crucified.” History provides no coroner’s report, no painstaking medical reconstruction.

Perhaps our first Christian ancestors could not bear to say any more. They had seen men crucified. They could walk to the outskirts of town if they wanted to count the cost — in blood and pain and humiliation — of their salvation.

Unlike Christians through most of history, we today have not grown up with the experience of public executions and public torture. Still, like the family of any murder victim, we feel the need to know the truth about our Savior and brother — not least because we believe He died for our sake.

Over the past 20 years, a friend of mine, Pittsburgh surgeon Jack McKeating, has applied his professional skills to this problem — reviewing the historical and archaeological evidence in light of recent medical research. Some years back, I interviewed him on the subject for Our Sunday Visitor newspaper.

“Any serious Christian has to take an active interest in the passion of Jesus Christ,” McKeating told me. “Unfortunately, we’re often too dispassionate about it. We tend to think of it in unreal terms, as an abstraction. But it involved a real person who underwent an absolutely brutal experience out of love for me.”

McKeating traces his interest to the late 1980s, when he was away from home on a fellowship in surgical oncology.

“I was in a Bible study with three other surgeons,” he recalled, “a fundamentalist, a Methodist, a Baptist and me.” One morning, one of his colleagues brought “On the Physical Death of Jesus Christ,” a 1986 study from the Journal of the American Medical Association.

That study gathered the descriptions of crucifixion from ancient sources. It analyzed the skeletal remains of crucified men, and it considered all the data in light of current medical research.

The JAMA study led McKeating to the classic text in the field, A Doctor At Calvary, an exhaustive account written by French Catholic surgeon Pierre Barbet. Barbet completed his book in 1949 after decades of research.

McKeating praises both studies for their scholarship and their unflinching care.

“Anyone who studies the matter has to start with these sources,” he said. “But keep in mind that it is a start. As we advance in medicine, we are able to learn still more about our Lord’s passion.”

How did crucifixion usually happen? Applying their medical knowledge to the historical data, doctors such as McKeating, Barbet and the JAMA team have attempted to reconstruct the events.

The ancient Romans had a special genius for torture. It helped them keep order in a vast empire. The public spectacle of extreme suffering — repeated with some regularity — served as a deterrent to would-be rebels and insurgents.

Crucifixion was the utmost refinement of the Roman art of torture. The Jewish historian Josephus called it “the most wretched of deaths.” It was designed to cause the most pain in the most parts of the body over the longest period of time.

Crucifixion was humiliating, too, so it was usually reserved for slaves, lower-class criminals or those whose crimes were especially heinous. The stripped man was exposed, naked, to a boorish crowd that delighted in such spectacles. They cast stones at him, spat at him, jeered at him.

The end began when executioners extended the condemned man’s arms and bound them to a wooden beam. Sometimes, they would also drive nails through the man’s wrists at the highly sensitive median nerve. The executioner relied on the element of surprise for the first hammer blow. The victim was unlikely ever to have experienced such pain before. It was “the most unbearable pain that a man can experience,” Barbet concluded.

Nailing the second arm, however, could pose a problem, because the nervous system would instinctively recoil from any repetition of that pain. The executioner would need to struggle against an arm rigidly resistant to his efforts. All of this wrangling, involuntary on the part of the victim, would intensify the pain in the arm already nailed.

The beam then was attached to a pole. Every shift of the beam renewed the pain in the median nerve. But all of that was just a prelude to the real torture of crucifixion.

The victim found himself suspended above the ground, his body slumped forward, his knees bent and his feet positioned as if he were standing on tiptoe. That position made it almost impossible for him to draw a breath.

“Crucifixion stretches the chest cavity open,” McKeating explained, “and the weight of the body pulls down on the diaphragm so the lungs are kept open. It requires great effort to breathe in and even greater effort to exhale — which is normally a fairly passive process.”

The victim could not breathe inward or outward without lifting his body up by the nails in his wrists and pushing up on the nail in his feet. With every breath, then, he felt the coarse metal tearing at his nerves.

Gradually, his limbs cramped and weakened. As he was less able to lift himself up, he began, slowly, to suffocate.

A victim of crucifixion alternated between the panicked sense of asphyxiation and the searing pain of the nails in his flesh. Relief from one inevitably brought about the other.

In a strong man, this could go on for many hours, even days. If the Romans wanted to accelerate the process, they would break the victim’s legs so he could no longer push himself upward to take a breath.

“Jesus was probably a strong man,” McKeating said. “He was relatively young, He worked hard, and He tended to travel by foot. But by the time He reached Calvary, He had undergone many hours of preliminary tortures that alone might have killed him.”

In the Garden of Gethsemane, “His sweat became like drops of blood falling to the ground” (Lk 22:44). The JAMA article, following Barbet, attributes this to a phenomenon called hematidrosis or hemohidrosis — hemorrhaging into the sweat glands. This is a rare condition that occurs in people at the extremes of human emotion. It leaves the skin very tender and highly sensitive to pain.

Jesus would have keenly felt every blow as His captors “mocked him and beat him” (Lk 22:63). The beatings continued through long hours in which He was also forced to walk from one interrogation to another — before the Sanhedrin, before Pilate, before Herod and again before Pilate. The JAMA research concludes that He walked two-and-a-half miles during that sleepless night.

Pilate ordered Jesus to be flogged, and Roman flogging alone could kill a man. A typical whip of cords was studded with metal, sharp animal bones or shards of pottery. It was designed to bruise and tear the skin. Often, a man was whipped by two torturers, one on each side, while he was bound to a post or pillar. It was here that Jesus probably suffered His greatest blood loss.

His back, torn open by the Romans, then had to bear the rough wood of the crossbeam, which probably weighed 75 to 125 pounds. He had to carry the burden along an uneven roadway from Pilate’s praetorium to the hill of Calvary, a third of a mile. Surely, He fell often.

“Some people say that Jesus’ suffering was somehow easier because he was God,” McKeating said. “But that’s not so. Many theologians believe He suffered in a greater way because He had perfect knowledge of what was happening. Also, His senses would have been more acute and more sensitive to pain because they were not at all dulled, as ours are, by sin and self-indulgence.”

What killed Jesus?

“I think it’s multifactorial,” McKeating said. “I think the proximate cause of death was probably suffocation — asphyxia. But I think the end came relatively swiftly — just three long hours — because our Lord was probably in shock before He was actually crucified.

“After the exposure, the emotional duress, the severe beating and then the scourging, He was probably in Class 3 shock, out of a possible 4.”

A great physiologist once described shock as the rude unhinging of the cellular machinery of our bodies.

“The technical definition,” said McKeating, “is that it’s inadequate perfusion of blood to the tissues of our body.

Our bodies normally have five liters of blood. McKeating said that “in a typical Roman scourging, a man would have lost a liter and a half.”

Shock would have weakened Him and left Him anxious and confused, hastening the end.

The Gospels suggest other factors, McKeating said. “After Jesus died, the soldier’s lance thrust brought forth blood and water (Jn 19:34). Where did the water come from? Probably pericardial effusion. Fluid would have built up from internal injuries, pulmonary contusions, bruises, beatings, and it would have filled His chest cavity or the sac around His heart. Every time the heart would beat, then, it couldn’t expand the way it needed to, and it couldn’t fill up. Eventually, it would stop.”

Forensic scientists say that the better we know what killed someone, the more likely we are to find out who killed him.

Who killed Jesus? After a decade-and-a-half of study, McKeating doesn’t hesitate to respond.